Not all basketball skills are created equal.
Some can exist in unlimited quantities across lineups. There is no such thing, for example, as too much shooting, passing, or well-timed help defense. Other skills have diminishing returns though.
Deploying a great screen setter can be immensely valuable within an ecosystem that includes a talented pick-and-roll initiator or good shooters capable of flying off picks away from the ball. But having multiple high-level screeners on the court doesn’t really bring much to the table unless those players also have other useful skills (think Steph Curry setting a back screen off the ball and the chaos the threat of his shooting creates).